This invention relates to an air conditioning system comprising at least one water-cooling type air conditioning unit, a heat pump chilling unit and a cold and heat accumulating tank.
Heretofore, a water-cooling type or air-cooling type heat pump air conditioning unit has been in use in many applications to effect space cooling and space heating with increased efficiency. Generally, an air conditioning unit is operated for a longer period of time in the daytime than at night, and demand for electric power shows a marked increased when space cooling is effected in the daytime in summer, so that it sometimes happens that the supply of electric power is unable to meet the demand and a power failure might occur. When such situation takes place, the water-cooling type or air-cooling type heat pump air conditioning unit is unable, when used singly, to cope with the power failure at peak load. When space heating is performed by the air conditioning unit of the aforesaid type, the air conditioning unit usually has a heating load rate in the daytime which is about 50-70% of the maximum load rate early in the morning, so that an air conditioning unit should have an unreasonably high capacity if it is desired to meet all the load requirements with a single unit. This would be economically disadvantageous. To cope with this situation, the use of a heat accumulating tank has been proposed as means for operating the air conditioning unit economically with increased efficiency.
An air conditioning unit using a heat accumulating tank is disclosed, for example, in U.S. Pat. Nos. 3,411,571, 3,523,575, 3,808,827, 3,922,876, 4,077,464 and 4,242,873 and Japanese Utility Model Application Laid-Open No. 83654/74.
In the above mentioned Japanese Utility Model Application Laid-Open No. 83654/74, a chilling unit (water-to-water heat pump) and an air heating source heat pump are connected to the heat accumulating tank through a water line. This prior art arrangement is intended to provide a system capable of operating with a high degree of efficiency in effecting space heating and space cooling by using the same pressure ratio of the compressor of the air heating source heat pump under the two conditions of heating and cooling. However, no measures have been taken to cope with an interruption of power supply when space cooling is effected at peak load or an application of a high load when space heating is effected.